1. Field of the Invention
The invention relates to a technique for reducing the size of a transfer for a four-wheel drive vehicle.
2. Description of Related Art
U.S. Pat. No. 8,042,642 discloses a four-wheel drive vehicle in which a two-wheel drive mode or a four-wheel drive mode is selectively carried out. In the two-wheel drive mode, driving force is transmitted from a driving source to right and left main drive wheels. In the four-wheel drive mode, driving force is transmitted from the driving source to the right and left main drive wheels and right and left auxiliary drive wheels. In U.S. Pat. No. 8,042,642, a transfer for a four-wheel drive vehicle is used to output part of driving force, which is transmitted from the driving source to the right and left main drive wheels, to the right and left auxiliary drive wheels via a power transmission member, when the drive mode is changed from the two-wheel drive mode to the four-wheel drive mode.
The transfer for a four-wheel drive vehicle, which is described in U.S. Pat. No. 8,042,642, includes a ring gear, an input shaft and a disconnect mechanism. The ring gear is used to drive the power transmission member. The power transmission member is, for example, a propeller shaft. The input shaft receives part of driving force that is transmitted from the driving source to the right and left main drive wheels. The disconnect mechanism connects the input shaft to the ring gear or disconnects the input shaft from the ring gear. In the transfer for a four-wheel drive vehicle, the input shaft is released from the ring gear by the disconnect mechanism in the two-wheel drive mode, whereas the input shaft is connected to the ring gear by the disconnect mechanism in the four-wheel drive mode.